<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .box{
        width: 500px;
        height: 300px;
        border: 2px solid #111;
    }
    .boxs{
        width: 100%;
        height: 40px;
        background-color: #111;
        color: #fff;
        display: flex;
        justify-content: space-between;
        /* text-align: center; */
    }
</style>
<body>
    <div class="box">
        <div class="boxs">
            <div id="qqq">第一节课</div>
            <div id="qqq">第二节课</div>
            <div id="qqq">第三节课</div>
        </div>
        <div class="bbb">1111</div>
        <div class="bbb">2222</div>
        <div class="bbb">3333</div>
    </div>
</body>
<script>
    var x=document.getElementById('qqq')
    var w=document.querySelectorAll('.box .bbb')
    for(let i=0;i<x.length;i++){
        x[i].onmousemove=function(){
            w[i].style.display='block'
        }
        x[i].onmouseout=function(){
            w[i].style.display='none'
        }
    }
</script>
</html>